Patent GB-724279-A (GB)
Title: Method and apparatus for manufacturing artificial filaments
IPC: D01D5/04
Filed: 1951-12-21
Abstract: <PICT:0724279/IV (a)/1> <PICT:0724279/IV (a)/2> In the production of artificial filaments by melt-spinning a molten spinning material or by dry-spinning a solution of spinning material in a volatile solvent by extruding the spinning material or its solution respectively into a closed chamber and drawing the extruded filaments therethrough, a gaseous medium is continuously passed into the chamber at a point intermediate the ends thereof, the medium introduced is divided into two streams flowing towards opposite ends of the chamber, the streams are withdrawn from the chamber near each end thereof, at least one of the streams is directly recirculated to the chamber, and the temperature of the directly re-circulating stream or the temperatures of the directly re-circulating streams is, or are changed prior to its, or their introduction into the chamber.  In the application of the process to dry-spinning, a portion of the solvent-laden gaseous medium, e.g. air, continuously withdrawn from the chamber (an elongated spinning tube) at the spinneret end thereof is sent to a solvent recovery system while at the same time an equal amount of fresh air is continuously introduced into the circulatory system. The solvent-laden air is withdrawn from and fresh air admitted to the system at such a rate as to keep the proportion of solvent vapour in the mixture of air and vapour in the system below the explosive limit, while at the same time utilizing a minimum amount of fresh air.  As shown in Fig. 1, the spinning melt or solution is extruded through a spinneret 14 into a vertical spinning tube which comprises a chamber 4, jacketed tubular portions 5 having annular manifolds 6 inserted therebetween and an exit chamber 7. Heated air from heater 40 passes through conduit 41, valve 33, conduit 34 and manifold 6 into the spinning tube, where it divides into two streams V1, V2, passing up and down the tube respectively.  The air passing down the tube picks up solvent vapour from the filaments 19, passes into chamber 7 and via conduit 36 and valve 36a to the blower 37 and then through the heater 40 back to the spinning tube.  The valve 39 is adjusted to admit fresh air at a predetermined rate into the system to replace the solvent-laden air which is withdrawn from the top of the spinning tube and sent to the solvent recovery system.  The air passing up the tube is drawn past the spinneret through the openings 43 and conduit 44 by the blower 45 and passed through the solvent recovery unit 46a.  The air, freed from solvent vapours, is either exhausted through the conduit 80 and valve 81 or re-admitted to the spinning tube via conduit 46b and valve 46c, the valves 39 and 81 being closed.  The latter alternative is used when melt spinning into an inert gaseous cooling medium.  The tubular portions 5 of the spinning tube are provided with jackets 10 through which a heat-transfer medium is passed by means of p  conduits 11, 12, and the whole tube may be covered with a jacket of thermal insulating material 13.  The spinning tube has a portion 3a extending down into the exit chamber 7 in order to prevent the filament bundle 19 from being drawn out of its normal path by the stream of solvent-laden air passing to the opening 42. The sloping bottom wall 20 of the chamber 7 is provided with an opening 21 covered by a door 22 hinged at 23 and having a slot 24 registering with a portion 21a of the opening 21 to provide a discharge orifice for the filaments 19 passing to the godet 25. As shown in Fig. 3, air from the conduit 34 enters the annular chamber 35 of the manifold 6, passes via the annular opening 58 into the annular chamber 57 and thence via the circular openings 59 into the spinning tube.  The air is thus caused to enter the tube from all directions with equal force instead of striking the filaments from one direction only.  Another modification differs from that shown in Fig. 1, only in that the stream of air passing down the spinning cell is withdrawn by means of a blower from the lowermost of the manifolds 6 instead of from the filament outlet chamber 7, and that part of the stream of air passing up the spinning cell is withdrawn by the same blower through the second manifold from the top of the spinning cell.  The remainder of the stream of air passing up the spinning cell is withdrawn from the top thereof as shown in Fig. 1.  The two streams of air withdrawn from the manifolds by the blower join and are passed, together with a controlled proportion of fresh air, through a heater, and thence are returned to the spinning cell through the third manifold 6 from the top of the cell.  When the apparatus is used for melt spinning, a cooling medium is circulated through the jackets 10 surrounding the spinning cell and the heater 40 is replaced by a cooler.